Well logging apparatus



Sept. 22, 1964 R CLEMENTS ETAL 3,149,490

WELL LOGGING APPARATUS Filed Oct. 9, 1958 United States Patent O3,149,490 WELL LOGGING APPARATUS Roy J. Clements, Leon M. Evans, andJohn J. Havlik, Houston, and Billy H. Towell, Bellaire, Tex., assignorsto Texaco Inc., a corporation of Delaware Filed Oct. 9, 1958, Ser. No.766,212 6 Claims. (Cl. 73-151) This invention relates to apparatus foruse in well surveying, and more particularly, to apparatus for wellsurveying which may be utilized simultaneously with the drilling processof a borehole.

In the conventional method of logging a borehole, the log is obtainedwhile the drill operation is periodically interrupted, during whichperiod the drill pipe is removed and a logging instrument suspended by asteel-shrouded multiconductor cable is lowered into the borehole. As theinstrument penetrates different geological strata information in theform of electrical signals is transmitted from the bottom of theborehole to the surface through the conductor cable where it is recordedon a chart.

In order to eliminate the disadvantages encountered during theinterruption in the drilling process of a borehole, a method ofgeophysical prospecting has been developed which comprises drilling aborehole, simultaneously and continuously detecting a physical variablein the borehole, simultaneously and continuously recording in the holethe physical variable and simultaneously and continuously recordingindications of the depth at which the physical variable is beingdetected.

In accordance with this invention, apparatus has been developed for usein a logging while drilling operation which comprises a tubular memberor housing adapted to be inserted in a drill stem or string, preferablyin the vicinity of the drill bit, a sealed container or pressuretightcapsule disposed in and rigidly secured to the housing and adapted andarranged to permit the passage of fluid through the housing, aninstrument casing disposed within said pressure-tight capsule andmounted axially so as to be freely rotatable about the longitudinal axisof the housing, the mounting means of said casing including resilientmeans disposed between the instrument casing and the pressure-tightcapsule for eliminating or minimizing movement of the casing along thelongitudinal axis thereof with respect to the capsule.

In order that the invention may be more clearly understood and readilycarried into effect it will now be described more fully with referenceto the accompanying drawing in which the gure illustrates the apparatusof the invention.

In the figure there is shown a tubular housing or pipe 14 which ispreferably disposed in the lower portion of a drill stem or string of aborehole or Well drilling apparatus, preferably between the drill bitand drill collar thereof, which is used to drill a borehole 18traversing one or more formations of the earth, for example, 19. Asealed container or capsule 20 adapted to withstand pressures of atleast 14,000 pounds per square inch is disposed coaxially within thehousing 14 and is rigidly secured thereto by support pins or studs 21,which are preferably made of stress-proof steel. Theicapsule 20 includesa hollow cylinder 22 which is preferably made of stainless steel, andtop and bottom caps 24 and 26 respectively. The top and bottom caps 24and 26 of the capsule 20 threadedly engage the cylinder 22, cap 24preferably having a left hand thread and cap 26 preferably having aright hand thread. O-rings 40 are located between the caps 24, 26 andthe cylinder 22 to provide effective pressure seals for the capsule 20.Disposed in the top and bottom caps 24 and 26 along the axis of thecylinder 22 are thrust bearings 42 and 44 respectively. Disposed withinthe pressure-tight capsule 20 is an inner ice case 48 for housinglogging equipment, for example, a signal receiver and recorder 45, whichcomprises a hollow cylinder 50 and upper and lower end plates 52 and 54having support shafts 56 and 58, respectively, which are preferably madeof SAE No. 3140 heat treated alloy steel having a yield point of 130,000p.s.i. The shafts 56 and 58 are disposed along the axis of the innercase 48 and are adapted to be received by the thrust bearings 42 and 44,respectively, in the caps 24 and 26 to provide an arrangement forsubstantially isolating the inner case 48 from torsional forces in thehousing 14 and in the pressure-tight capsule 20, which forces may beapplied to the drill string at the earths surface in a rotary drillingprocess or in the borehole in a turbo drilling process.

The lower bearing 44 is essentially a ball bearing having an inner race162 upon which a shoulder 164 of the bottom support shaft 58 is seatedand an outer race 166 which is seated upon a shoulder 176 of the bottomcap 26. The top support shaft 56 of the inner case 48 is similarly heldin `the top cap 24 of the capsule 20 by the top thrust bearing 42. Thetop thrust bearing 42 is also essentially a ball bearing having an innerrace 163 and an outer race 167, a shoulder 165 of the upper cap 26 beingseated on the outer race 167 and the inner race 163 being seated on awasher 169, preferably a steel washer, which is in turn seated on ashoulder 171 of the top shaft 56. The thickness of the washer 169 may beselected so as to provide necessary clearance for expansion of the innercase 48 depending upon the anticipated range of temperatures in aborehole. Whenever high temperatures are anticipated in the borehole, athin washer may be used or the washer may be entirely eliminated, so asto provide room for expansion of the apparatus without binding thefreely rotatable inner case 48 between the top and bottom caps 24 and26. The washer can also be used to serve as an adjustment for slightdifferences in the lengths of various inner cases which may be used inthe pressure-tight capsule 20.

When the thickness of the washer 169 is such that clearance forexpansion of the inner case 48 is provided in the pressure-tight capsule20, the inner case 48 will tend to vibrate in the capsule 20 during thedrilling process whenever temperatures below the maximum temperaturesare encountered, thus producing forces in the inner case 48 in thedirection of the longitudinal axis thereof which could adversely affectthe logging equipment housed in the inner case 48. In order to eliminateor minimize the longitudinal vibrations, resilient means 173 aredisposed between the inner case 48 and the pressure-tight capsule 20 soas to oppose longitudinal forces which may tend to set up vibrations inthe inner case 48. The resilient means 173 preferably includes acompression spring 175, for example, a 2001b. compression spring,disposed in a chamber 177 in the top cap 24 of the pressure-tightcapsule 20 along the longitudinal axis of the inner case 48 between theend of the top support shaft 56 and end wall of the chamber 177. Thecompression spring is held in position in the chamber 177 by engaging atits upper end a spring retainer 181 and at its lower end a spring thrustplate 183. A second top thrust bearing 179 is disposed in the chamber177 of the top cap 24 along the longitudinal axis of the inner case 48between the end of the top support shaft 56 and the cornpression spring175 to eliminate or minimize the frictional forces between the spring175 and the top support shaft 56. The second top thrust bearing 179 isheld in position in the chamber 177 between the spring thrust plate 183and a top shaft thrust plate 185 which engages the end of the top shaft56. In order to prevent the compression spring 175 and the second thrustbearing 179 from sliding out of the chamber 177 in the top cap 24 whenthe top cap 24 is removed from the cylinder 22, a locking ring 187 and ajam nut 189 are secured to the top cap 24 by threadedly engaging the topcap 24 at the mouth of the chamber 177.

Accordingly, it can be seen that by utilizing a spring which has asuitable compressional force exerted on the upper end of the upper shaft56 the inner case 48 will be prevented from jarring against itssupporting apparatus.

In order to rigidly connect the capsule 2@ to the housing 1d a number ofthe support pins or studs 2l, for example, twelve pins, are welded atsuitable points to the outside surface of the capsule and a like numberof holes or openings 173 are drilled through the housing i4 at pointswhich are spaced so as to be aligned with the welded pins 2l when thecapsule 2.0 with the welded pins 21 is inserted into the housing lid.After the pins Zi are aligned with the openings 17S each pin is weldedto the housing 14 through its corresponding opening and each of theopenings 178 is filled with the weld so as to provide a housing with asmooth exterior surface.

The inner case and the pressure-tight capsule Ztl have been constructedso that the inner case 48 can be easily inserted into and removed fromthe pressure-tight capsule 2t). When `the inner case i3 is placed in thecapsule 20, the bottom shaft 53 is received in the bottom thrust bearing44 with the shoulder i64- of the bottom shaft 53 engaging the bearingda. The top cap 24 with the top thrust bearing ft2, which receives thetop shaft 56, and the resilient means 173 is placed over the top shaft56 and secured to the cylinder 22 of the capsule 2li. The top and bottombearings i2 and la and the top and bottom shafts 56 and 53 are disposedon the longitudinal axis of the tubular pipe M. Accordingly, it can beseen that the arrangement of this apparatus supports the inner case 48in a manner which will protect sensitive logging equipment from angularshock or excessive angular acceleration or deceleration.

It should be understood that the apparatus of this invention may beinserted in a rotary drill string or in a turbo drill string. When theapparatus of this invention is used in a rotary drill string, it ispreferably inserted between the drill bit and the lowermost drillcollar. When the apparatus is used in a turbo drill string it may beinserted between the driil pipe and the turbine, or if it is desired toplace the logging equipment closer to the drill bit the apparatus may beinserted in the turbo shaft between the turbine and the drill bit.

When the drill string including the well surveying apparatus iscompletely assembled the drill bit may be rotated by a suitable primemover in the usual manner since the housing ltd has been designed towithstand forces which are equal to or greater than the rated strengthof other sections of the drill string. Furthermore, the mud flow throughthe drill string is not substantially retarded by the apparatus sincethe cross-sectional area of the mud duct between the inner surface ofthe tubular housing M and the external surface of the capsule Ztl isequal to or greater than the cross-sectional area of the opening througha conventional drill collar.

Since the drill string is withdrawn from the drill hole approximatelyonce every 24 hours in rotary drilling operations, and more frequentlyin turbo drilling operations, in order to inspect or remove the drillbit, the record or log produced by the logging equipment disposed in theinner case d8 can be viewed at least once every 24 hours with a minimumof disturbance in the drilling operation. Each time that the bit istaken out of the hole the drill stem is broken at the joint at the upperend of the housing ill, i.e., at the joint nearest to the top cap 24 ofthe capsule Ztl. The top cap 24 is then removed from the capsule Ztl andthe inner case is withdrawn from capsule Ztl. The top end plate 52 maythen be removed from the cylinder 5i) of the inner case and the loggingequipment withdrawn from the inner case 58.

It should be understood that logging equipment, such as that whichprovides radioactivity, vibration, or temperature logs, may be disposedwholly within the inner case 48. However, this apparatus may also beutilized when a sensing element is required outside of the inner case48, capsule 2li or the housing 14, for example, as when pressure, r.p.m.of drill bit, self potential or resistivity logs are desired. It shouldalso be understood that in order to obtain resistivity logs of theborehole simultaneously with the well drilling operation electrodessuitably connected to the recorder ,must be disposed at the outersurface of the housing 14 and suitably insulated therefrom. Furthermore,the short circuit effect of a metallic housing must be taken intoconsideration when resistivity logs are being produced. Such resistivitylogging while drilling systems are described more fully in the copendingapplication of Clements, Lee and Stelzer having Serial No. 677,969, ledAugust 13, 1957, and entitled Geophysical Prospecting Apparatus.

Accordingly, it can be seen that this invention provides rugged loggingapparatus which may be readily located in the drill string near thedrill bit to log the subsurface formations or the boreholesimultaneously with the drilling process. Although the apparatus of thisinvention is utilized under severe requirements of heat and mechanicalvibration and shock at the point of drilling, the apparatus is soconstructed that even DArsonval-type galvanometers may be successfullyemployed in the recording circuit of the logging equipment.

Obviously, many modifications and variations of the invention ashereinabove set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be employed asare indicated in the appended claims.

We claim:

1. Apparatus comprising a tubular member adapt-ed to be coupled in adrill string in the Vicinity of the rotatable drill bit, apressure-tight capsule disposed within and rigidity secured to saidtubular member, `an inner case including apparatus for conducting a login the borehole disposed within said capsule and means for mounting saidinner case within said capsule for substantially free rotation thereinabout the longitudinal axis thereof, said longitudinal axis of saidinner case being disposed substantially along the longitudinal axis ofsaid drill string, said mounting means including resilient meanscomprising a spring mounted in compressional relationship between saidcapsule and said inner case and being oriented to apply pressure betweensaid capsule and said inner case along said longitudinal axis, therebycomprising means for opposing upward movement of said inner case alongthe longitudinal axis thereof with respect to said pressuretightcapsule, thereby substantially to eliminate longitudinal chatter whilemaintaining said housing freely rotatable.

2. Apparatus for well logging comprising a tubular member adapted to becoupled in a drill string in the vicinity of the drill bit, apressure-tight capsule disposed within and rigidly secured to saidtubular member so as to provide `a iiuid passage through said tubularmember, an inner case including apparatus for conducting a log in theborehole disposed within said capsule and means for supporting saidinner case within said capsule so as to permit said inner case to befreely rotatable therein about the longitudinal axis of said tubularmember, said supporting means including a compression spring mounted incompressional relationship between the upper end of said capsule andsaid inner case and characterized in that the opposing force thereof isdirected along said longitudinal axis in a given direction, thereby tooppose movement of said inner case along said longitudinal axis withrespect to said pressure-tight capsule.

3. Apparatus as defined in claim 2 further comprising bearing meansdisposed between said spring and said inner case for preventingrotational forces from being transferred between said spring and saidinner case.

4. Apparatus comprising a tubular member adapted to be coupled in adrill string in the vicinity of the drill bit, a pressure-tight capsuledisposed within and rigidly secured to said tubular member in spacedrelation thereto so as to provide a fluid passage through said tubularmember, said capsule having rst and second caps at opposite ends thereofrespectively, an inner case including apparatus for conducting a log inthe borehole disposed within said capsule, said inner case having afirst support shaft at one end thereof and a second support shaft at theopposite end thereof, and means for supporting said inner case withinsaid capsule so `as to permit said inner case to be freely rotatabletherein about the longitudinal axis thereof, said supporting meansincluding first and second thrust bearings disposed within said rst andsecond caps respectively and adapted to receive the first and secondshafts respectively of said inner case, said supporting means providingpredetermined clearance for expansion of said inner case when operatedover a predetermined temperature range, and a compression springdisposed within said rst cap and oriented to apply a force on the end ofthe support shaft along the longitudinal axis of the inner case, and anend thrust bearing disposed within said rst cap between the end of saidrst shaft and said compression spring.

5. Apparatus as dened in claim 4 wherein said first shaft is providedwith a shoulder and which further includes a washer having a giventhickness and disposed on said first shaft between said first thrustbearing and said shoulder of said shaft.

6. Apparatus for well surveying comprising a tubular member adapted tobe inserted in a rotatable drill string, a housing disposed within saidtubular member so as to provide a iiuid passage through said tubularmember, logging equipment disposed within said housing and means formounting said housing within said tubular member for substantially freerotation therein about the longitudinal axis of said tubular member,said mounting means providing predetermined clearance for expansion ofsaid inner case along said longitudinal axis when operated over apredetermined temperature range, said mounting means further includingresi-lient means comprising a spring mounted in compressionalrelationship between said capsule and said inner case and being orientedto apply pressure between said capsule and said inner case along saidlongitudinal axis thereby comprising means for opposing movement of saidhousing along the longitudinal axis of and with respect to said tubularmember thereby substantially to eliminate longitudinal chatter whilemaintaining said housing freely rotatable.

References Cited in the le of this patent UNITED STATES PATENTS2,313,168 Opocensky Mar. 9, 1943 2,364,908 Miller Dec. 12, 19442,401,606 Brown June 4, 1946 2,658,284 Arps Nov. 10, 1953 2,680,901Kaiser June 15, 1954 2,728,554 Goble Dec. 27, 1955 2,804,281 Osburn Aug.27, 1957 2,808,231 Kimbrell Oct. 1, 1957 2,848,710 Owen Aug. 19, 19582,850,264 Grable Sept. 2, 1958 3,016,960 Hall Jan. 16, 1962

1. APPARATUS COMPRISING A TUBULAR MEMBER ADAPTED TO BE COUPLED IN ADRILL STRING IN THE VICINITY OF THE ROTATABLE DRILL BIT, APRESSURE-TIGHT CAPSULE DISPOSED WITHIN AND RIGIDITY SECURED TO SAIDTUBULAR MEMBER, AN INNER CASE INCLUDING APPARATUS FOR CONDUCTING A LOGIN THE BOREHOLE DISPOSED WITHIN SAID CAPSULE AND MEANS FOR MOUNTING SAIDINNER CASE WITHIN SAID CAPSULE FOR SUBSTANTIALLY FREE ROTATION THEREINABOUT THE LONGITUDINAL AXIS THEREOF, SAID LONGITUDINAL AXIS OF SAIDINNER CASE BEING DISPOSED SUBSTANTIALLY ALONG THE LONGITUDINAL AXIS OFSAID DRILL STRING, SAID MOUNTING MEANS INCLUDING RESILIENT MEANSCOMPRISING A SPRING MOUNTED IN COMPRESSIONAL RELATIONSHIP BETWEEN SAIDCAPSULE AND SAID INNER CASE AND BEING ORIENTED TO APPLY PRESSURE BETWEENSAID CAPSULE AND SAID INNER CASE ALONG SAID LONGITUDINAL AXIS, THEREBYCOMPRISING MEANS FOR OPPOSING UPWARD MOVEMENT OF SAID INNER CASE ALONGTHE LONGITUDINAL AXIS THEREOF WITH RESPECT TO SAID PRESSURETIGHTCAPSULE, THEREBY SUBSTANTIUALLY TO ELIMINATE LONGITUDINAL CHATTER WHILEMAINTAINING SAID HOUSING FREELY ROTATABLE.